This paper attempts a brief summary of the structure of the Northern Pennines for geologists and geographers, especially for those who are interested in the relation of geographical form to geological structure. It is, for the most part, a re-statement, and advances little that is new; but it is thought that the present visit of the Association to the North may be a fitting opportunity to summarize our knowledge of the structure of an interesting region, especially as considerable progress has been made in our detailed knowledge of the Northern Pennines since the visit of the Association to Newcastle in 1889.